1. Field of the Invention
The invention relates to a four-point contact bearing which includes balls, ball races and cage segments.
2. Description of the Prior Art
Four-point contact bearings including balls held apart by a cage or other structure have been used for many years. For example, there are swivel bearings, in which the balls are held apart by so-called intermediate pieces. Rim slots, used in some other bearings, are not used in these swivel bearings, in order that the bearing rings have high shoulders and the raceways may have large pressure angles. Large axial forces and tilting moments may be transmitted through the bearing, but the different ball speeds resulting therefrom are not taken up by the intermediate pieces, so that circumferential forces result which brake the balls against the intermediate pieces. The braked or decelerated balls slide on the raceways, increasing wear. Furthermore, the decelerated balls produce a pile-up of balls, so that the circumferential braking force increases further. This accumulation of circumferential forces results in a "bottle-neck effect", causing the bearing moment of rotation to vary greatly. The use of a four-point contact bearing with such intermediate pieces is therefore limited to swinging movements with small angles of swing, since bottleneck effects can begin to occur upon swinging movements of more than 180.degree..
Furthermore, the intermediate pieces used in such bearings have a shape which makes them difficult to form as an injection molded part, so that they tend to break due to the internal stresses and forces which occur in operation. Intermediate pieces are therefore for the most part cut from semifinished articles, which is a very expensive and cumbersome process.
In order to avoid these disadvantages, it is possible to use a four-point contact bearing with a cage for the balls. The cage is shaped like a ring or is comprised of a plurality of ring segments, which are disposed together to form a cage ring. The cage has a relatively large cross-section for stability and is guided in the rim gaps between the rings. Each cage segment may, for instance, cover more than one ball, so that the segment is held by the balls and cannot twist. As a result of the relatively large width of the rim gap required for the cage, the travel grooves or raceways for the balls are reduced in size. Therefore, large pressure angles for the transmission of predominantly axial loads are not possible in the races. For this reason, such a bearing design is limited to use in predominantly radially loaded four-point contact bearings.